Sine Rule q

If A = 18degrees, b - a =2, ab =4, using the usual notation fora triangle, use the sine rule to find B.
Help I keep getting this q wrong in my book it says the answer is 53.85, but i keep getting like 53.999.

If A = 18degrees, b - a =2, ab =4, using the usual notation fora triangle, use the sine rule to find B.
Help I keep getting this q wrong in my book it says the answer is 53.85, but i keep getting like 53.999.